DrZee-soilcorrosivityNACE

7/23/2019 DrZee-soilcorrosivityNACE

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Soil Corrosivity andCorrosion Control

Dr. Zamanzadeh (Zee)

Geoff Rhodes

Matco Services, Inc.Octoer !th, "##$


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O%tline

&' Introd%ction

"' Soil Characteristics

' Soil Corrosivity

' *arameters effect soil corrosivity

+' Soil corrosion rate

' Corrosion Ins-ection

' Corrosion Control

!' Cathodic *rotection

$' / 0 1


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2istory&34arly Cent%ry' all corrosion -rolems 5as attri%ted to stray

c%rrents from trollly cars, and s%5ays.

"3&$ con6ress a%thorized 78S(7ational 8%rea% of Standards toinvesti6ate stray c%rrent -rolems

38y &$"# they fo%nd o%t that yo% do not need to have stray

c%rrents to have corrosion -rolems

3&$+ 78S concl%ded that soil corrosion is too com-le9 to -ermitcorrelation 5ith any one -arameter. 49tensive data 5as -rovided at

this time for many soil conditions and metals


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Predicting Soil Corrosivity

7at%ral Reso%rces Conservation Service

&$ e9tensive soil testin6 -erformed on over

",## soil ty-es in :nited States

Soils descried y horizon (layer), str%ct%re,

color, or6anic content, -2, 5ater tale,

to-o6ra-hy, and chemical;mineral content.


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Predicting Corrosivity of

Soils:tility =o5ers, *oles,


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Why Do We Need to Predict Soil

Corrosivity?

4arly corrosion -revention

S-ecify coatin6s, cathodic -rotection, or

alternate materialsS-ecify ins-ection and maintenance

intervals for %ried str%ct%res and %tilities


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Soil Chemistry1- Mineral soils are a group of primarily inert

combinations of oygen! aluminum! silicon! and

iron "and other metals#$

%- &he primary constituents of over '() of soils are*

+ Poly silicates* "Si,

'

.-# / 0! l! or Na

+ rthosilicates* "Si..-# / 0!2!3!Ca! 4e! or

+ Metasilictes* "Si,%-# / Ca! Mg! 5$

+ ides* "Si%! 4e%,! 4e,.#

+ Calcite* "CaC,#

+ 2ydrous luminum Silicates "Clays#* "l 2y# "Siy#

,- rganic matter is another constituent

.- Corrosive 6onics* Chlorides! Sulfates! Sulfides


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What 4actors ffect Soil

Corrosivity?

@ Chloride level

@ Moist%re content

@ O9y6en content;Redo9 -otential

@ Soil -ermeaility;te9t%re

@ -2;1cidity @ =em-erat%re

@ Soil resistivity

@ Draina6e characteristics@ S%lfate and S%lfite ion concentrations

@ Microiolo6ical activity

@ Stray c%rrents, 4lectrochemical *otential Aields

@ S-illa6e of corrosive s%stance;-oll%tion

3 16ric%lt%ral chemical activities


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Soil &esting + Soil Classification

Classification -er 1S=M D"! 0 D"!!

Soil str%ct%re'

Gravel (Coarse -articles @ retained on B sieve)Sand (Coarse -articles @ retained on B"## sieve)

Silt 0 Clay (Aine -articles @ -assin6 B"## sieve)

Color

Star7 color changes indicate reducing soils

Dar7 colors indicate organic matter

3ight colors indicate mineral leaching


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Odor

Or6anic smells may indicate iolo6ical activity

S%lf%ro%s smell may indicate microiolo6ical activity

@ -artic%larly anaeroic acterial activity

*lasticity

2i6h to moderate -lasticity indicates hi6h 5ater

holdin6 ca-acity o5 -lasticity indicates -oor 5ater holdin6 ca-acity


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Structure: Clay + siltColor: Homogenous, darkbrownOdor: Slightly organicPlasticity:High

Corrosivity: Moderate tolow depending on ioncontent & pHlater found tohave neutral pH and lowchloride content; lowcorrosivity


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Soil Characteristics (clay and sand)

1- Clay has the finest particle si8e 9hich reduces movement of air

"oygen# and 9ater! i$e$ lo9 aeration 9hen 9et$ &his may lead to

very lo9 general corrosion! but increase local "pitting# corrosion by

setting up differential aeration cells$

%- 2o9ever the high plasticity "stic7iness# of clay during shrin7-s9ell

of the soil can pull off susceptible coatings$

,-Clay also is susceptible to crac7ing during 9et-dry cycling 9hich

can help transport air and moisture do9n to the pipe surface$

.-Sand promotes aeration and moisture distribution$ Soluble salts

and gases "air:oygen# can are more easily transported to the

metal surface$ &his may lead to greater general corrosion but also

produce less pitting$


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Soil Classification per ;SCS


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Soil &esting

Soil Resistivity =estin6'

In3Sit% Soil Resistivity @ 3*in


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Soil &esting

In3Sit% Soil Resistivity =estin6


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Soil &esting

aoratory Minim%m Soil Resistivity =estin6

E+## ohm3cm 49tremely corrosive

+##3&,### ohm3cm Fery corrosive

&,###3",### ohm3cm Moderately Corrosive ",###3,### ohm3cm Mildly Corrosive

,### ohm3cm *ro6ressively lo5er corrosivity


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&!

Color and 1eration

2i6h levels of acteria can cons%me the

o9y6en -resent in the soil

8acteria Cons%me O"*oor 1erated

2ot3di- 6alvanized steel 5ill not -erform as

5ell in soils containin6 lar6e amo%nts of

or6anic acteria


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&$

=ime of


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"#

*article Size

Controls aeration and time of 5etness cate6ories of -article size for soils

Sand (#.# 3 " mm )

Silt (#.##+ 3 #.# mm)

Clay (E #.##+ mm)


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"&

Color and 1eration

Sim-lest method of characterization Red, ello5 and 8ro5nO9idized Ae


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/%estions to e asJed

Does corrosion ta7e place?

6f it does! ho9 fast? 3ife epectancy?

2o9 can 9e control the rate of corrosion?


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Immunity, Cathodic Protection

Corrosion

tability Diagram For Iron


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Soil &esting +


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Corrosion Rate

=est co%-on

Resistance *olarization

=afel a5Dynamic *olarization

4IS

*hysical Meas%rements


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Aail%re 49am-les


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:tility, Comm%nication =o5er

Str%ct%res

1nchor Rods

Galvanized *oles and =o5ers

Co--er Gro%ndin6


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CS

raphiti8ation*Cast 6ron Water Main

@rittle 4ailure


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*hoto6ra-h sho5in6 the lon6it%dinal cracJ

in the -i-e.


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*hoto6ra-h sho5in6 the transverse sa5 c%t thro%6h the

-i-e at a location &+ inches from the end of the -i-e

Corrosive soils, Clay, 2i6h Salt Content Soils and MIC lo5 -2

*h t h h i th t d


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*hoto6ra-h sho5in6 that secondary

cracJin6 5as confined to the corroded areas

of the -i-e.


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More Aail%res

Aail%re of =o5ers in flooded valley, "##&

Similar incident in 8C "##"

Aail%re of anchor rods "##

Aail%re of anchor rods "##+

2i6h chloride content 0 lo5 -2Fery hi6h chloride content 0 hi6h -2


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ocalized Corrosion 1ttacJ at a load earin6 memer

Direct 8%rial :tility =o5ers


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49tensive ocalized Corrosion

S%s-ect *otentials


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Galvanized 1nchor Rod

1ove Gro%nd

:nder6ro%nd

Co--er Gro%ndin6

Soil 4nvironment


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Corrosion

Galvanized 1nchor Rods

Aail%re

Corrosion


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Shiny vs. D%ll

Galvanized Steel

G l i d St l


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Galvanized Steel

A%ndamental Mechanisms

8arrier

Cathodic *rotection


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Methods of *rotectin6 Iron and Steel

8arrier *rotection Isolates metal from the environment M%st adhere to the ase metal M%st e resistant to arasion

Cathodic *rotection Chan6e electrochemistry of corrosion cell 8ased on the electrochemical series Ins%re ase metal is the cathodic element


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Staility of Galvanized Steel

O9y6en,


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Zinc (6alvanized)

Staility


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I7S*4C=IO7 of =o5er Gro%nd

1nchors


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OKectives of Ins-ections


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Ins-ection =echniH%es

Fis%al

49cavation and Fis%al Ins-ection

7on3destr%ctive techniH%es(so%nd, 4M>)

4lectrochemical =echniH%es

DesJ St%dy

=ier =estin6 Ins-ectionAreH%ency of Ins-ection


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49cavations33Sho%ld I Di6("ft)?Common Industry Practice

7e6ative Aactors aor intensive Inherently dama6in6 InadeH%ate vis%al e9amination Safety com-romised d%rin6 fill removal =renchin6 re6%lations

Diffic%lt to re-eat

1 h R d C i


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1nchor Rod Corrosion

Scenarios

Corrosive Soil or 8acJfill

Galvanic effectsStray C%rrents


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Corrosion of 1nchor Rods

Determine -resence of active corrosion' 2i6hrisJ areas

Determine a--ro9imate corrosion rate

S-ecific recommendation'

a) Immediate action'& to 3 + to years

) 7o action, Cathodic *rotection 0 Coatin6,


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Lno5led6e 8ased Ins-ection

1 Jno5led6e ased assessment -lan is critical to an effective andaffordale asset mana6ement -ro6ram.

Lno5led6e 8ased Ins-ection can identify the most criticalcom-onent(s) ased on o-eratin6 stresses and corrosionmechanism (s)

=o ens%re that they are maintained at a condition aove the criticalthreshold

8enefits of Lno5led6e 8ased


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8enefits of Lno5led6e 8ased

Ins-ection8y eliminatin6 ins-ection tasJs that

contri%te little to risJ mana6ement and

miti6ation

Defines c%rrent condition

Deterioration rate

*erformance reH%irements

Reliaility thresholds


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Ins-ection

*hoto6ra-hic doc%mentation*otential meas%rementsSelection of anchor rod*hoto6ra-hic doc%mentation*otential ma--in6Soil resistivity meas%rements de-thsGeneral Oservations' Gro%ndin6 iss%es, corrosion oservations, -aint -rolems,site -rolems, mechanical dama6e, concrete -rolems and corrosion in concrete

49cavationDimension 0 coatin6 meas%rementSoil testin6' dry and 5et, corrosion rate, ZR1>.Com-%terized data entryRevie5 y team leader, Matco -roKect mana6er and Dr. Zee

Recommendations' Re-air, Re-lacement or no action. Cathodic *rotection


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*hoto6ra-hic Doc%mentation


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8: B !"##+


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!##"+!##"+ .N*G
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=estin6 -er 1S=M G&

Will determine native potentials of copper,

steel, and zinc in the soil near the anchor.

Will determine mixed potential and

corrosion current between copper-steel and

copper-zinc when coupled in moist soil.


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Soil Resistivity

4-pin Wenner method per S!" #$%

&ins spaced at 'ft and ()ft *spacing + a


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1dditional Data

Dry and sat%rated soil resistivity in the la

ZR1

Corrosion rate

Soil sam-les


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Recommendations

*erform soil resistivity and electrochemical -otential

Determine 6alvanic corrosion rateRate the corrosion attacJ ased on the aove-erformance -arametersDetermine electrical contin%ity and 6ro%ndin6Desi6n C* -er 71C4 Standards4stalish criteria for acce-tanceC* sho%ld e desi6ned y 71C4 CertifiedCorrosion S-ecialist and meet 71C4reH%irements

Considerations for 1--lication of


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Considerations for 1--lication of

Cathodic *rotection*otentials more nole than 3#.#Corrosive soils16e years

Soil resistivities E +### ohm3cm

Galvanic c%rrent "## to +## micrometersCl &+# --m*resence of stray c%rrents, interfernce or e9tensive co--er 6ro%ndin6


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S%mmary

=he corrosion eval%ation -rotocol sho%ld e ased %-oncorrosion en6ineerin6 f%ndamentals and -rovides a aseline for f%t%re ins-ection

=he a--roach can e a--lied to all ty-es of soilformations

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